The present invention relates to wires comprising molybdenum and tantalum which have utility for lighting applications and for electrical resistant heating wires.
The prior art discloses lead-in wires of molybdenum which are capable of being sealed within glass materials so as to prevent contamination of an envelope with air or other gases present in an operating atmosphere.
Gettering is a process by which the purity of a vacuum or the content of the envelope is maintained at a desired purity. Flash getters are employed as chemically active metals evaporated on the walls of a vacuum enclosure to provide a large area for reaction with a gas. Bulk getters are run hot but not flashed. Tantalum is disclosed in the prior art as a getter for lamps.
U.S. Pat. No. 3,748,519 to Martin et al. discloses a lead-in assembly having a molybdenum component and a tantalum gettering component attached to the lead-in assembly.
U.S. Pat. No. 3,676,083 to Cheney et al. discloses a molybdenum base alloy having a recrystallization temperature above that of molybdenum.
U.S. Pat. No. 3,644,773 to Coaton et al. relates to a hydrogen and halogen filled incandescent lamp having a hydrogen absorbing structure in the form of a getter flag comprising a piece of titanium coated with paladium. Tantalum is also disclosed as being used in place of titanium.
U.S. Pat. No. 3,983,440 to Scott et al. describes a structure in the form of a hollow carrier body of refractory metal in which a source of halogen, metal or metal halide is disposed and may be covered by a closure of refractory metal which may have gettering properties. The closure may be titanium, tantalum or zirconium or niobium.
When using alloy wires of molybdenum and tantalum in high temperature applications such as described above, it is desirable for the wires to retain the desired properties of high tensile strength and good ductility. However, it has been found that high temperature use, which results in recrystallization, decreases ductility which may cause mechanical failure.
It is an object of the present invention to provide a wire having favorable properties for use in prolonged high temperature applications.
Other and further objects will become apparent from reading the following description.
In accordance with the principles of the present invention, there is provided an alloy wire consisting essentially of molybdenum, tantalum and a sufficient amount of minor ingredients for maintaining favorable ductile and tensile strength properties after recrystallization, said minor ingredients and impurities being less than about one percent by weight.
There is also provided a method for producing an alloy wire consisting essentially of molybdenum, tantalum and minor ingredients comprising intimately mixing molybdenum powder, tantalum powder, and minor ingredients to form a uniform powder blend consisting essentially of molybdenum, tantalum, and a sufficient amount of minor ingredients for maintaining favorable tensile strength and ductility after recrystallization, said minor ingredients and impurities being less than about one percent by weight, forming a compacted article from said powder blend, sintering said powder blend for a sufficient time and at a sufficient temperature to form a resulting article, said sintering being carried out to such an extent wherein said article when cooled consist essentially of a single phase solid solution, working said article to form an alloy wire, and heating said wire for a sufficient period of time and at a sufficient temperature for recrystallizing said alloy.